Methods of recycling and compositions used therein

ABSTRACT

In one embodiment, the present invention relates to a method of separating a coating from a base plastic in a multilayered structure, comprising the steps of (A) providing the multilayered structure comprising at least a coating and a base plastic; (B) contacting the multilayered structure with a mixture comprising (i) a major amount of water, (ii) at least one basic compound or acid compound, (iii) at least one lifting agent, and (iv) at least one accelerator; and (C) separating the coating from the base plastic. In another embodiment, the present invention relates to a separating composition containing a major amount of water, at least one basic compound or acid compound, at least one lifting agent, and at least one accelerator. The inventive methods and compositions overcome numerous problems in the art by enabling the efficient recycling of coated polymer articles whereby clear and/or colorless recycled polymers may be obtained.

FIELD OF THE INVENTION

The present invention relates to a method of separating polymer layersof a multilayered structure, a method of recycling coated polymerarticles and compositions used in the methods.

BACKGROUND OF THE INVENTION

Plastics are used in diverse applications including containers,clothing, carpet materials, fiberfill and a multitude of otherapplications. In order to enhance the performance of plastics in certainapplications, a coating may be applied to the plastic. A plastic may becoated to improve its strength, its permeability or anothercharacteristic. For example, a barrier coating can be applied to thinwalled plastic food and beverage containers thereby decreasing thepermeability of the plastic to gas, such as carbon dioxide gas or oxygengas. This is because food and beverage containers have a relativelyshort shelf life due to the entry of oxygen and loss of carbonationthrough the thin container walls. Barrier coated food and beveragecontainers exhibit a 10 to 30 fold shelf life increase over uncoatedcontainers.

For several reasons, including cost effectiveness and environmentalconcerns, plastics are recycled. However, plastics having a coatingcannot be efficiently recycled in some instances. This is particularlyapparent for plastics having a barrier coating because thebarrier-coated plastic becomes discolored or unclear upon melting.Recycled plastic which is discolored or unclear cannot be used toproduce clear, colorless fibers, containers or other products unlessthey are subjected to extensive and additional processing. As a result,there is a need to remove coatings from plastic prior to recycling.

SUMMARY OF THE INVENTION

In one embodiment, the present invention relates to a method ofseparating a coating from a base plastic in a multilayered structure,comprising the steps of (A) providing the multilayered structurecomprising at least a coating and a base plastic; (B) contacting themultilayered structure with a mixture comprising (i) a major amount ofwater, (ii) at least one basic compound or acid compound, (iii) at leastone lifting agent, and (iv) at least one accelerator; and (C) separatingthe coating from the base plastic. In another embodiment, the presentinvention relates to a separating composition containing a major amountof water, at least one basic compound or acid compound, at least onelifting agent, and at least one accelerator.

In yet another embodiment, the present invention relates to a method ofrecycling coated polymer containers including the steps of providing apolymer container having a polymer coating, preparing flakes from thecoated polymer container, contacting the flakes with a mixturecontaining a major amount of water, at least one basic compound or acidcompound, at least one lifting agent and at least one accelerator, andseparating the mixture and the polymer coating from the flakes. Theflakes may be extruded into polymer articles suitable for use as food orbeverage containers.

The inventive compositions and methods overcome numerous problems in theart by enabling the efficient recycling of coated polymer articleswhereby clear and/or colorless recycled polymers may be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general representation of a method of recycling coatedpolymer articles according one embodiment of the invention.

DETAILED DESCRIPTION

In the following description, a number of features and parameters aredescribed, defined and/or exemplified with one or more numerical valuesin a range. Any combination of the values of the ranges described hereinmay be used. For instance, the higher value of one specific range may becombined with the lower value of another specific range to describe anadditional range of values.

The term "hydrocarbyl" includes hydrocarbon as well as substantiallyhydrocarbon groups. Substantially hydrocarbon describes groups whichcontain heteroatom substituents which do not alter the predominantlyhydrocarbon nature of the group. Examples of hydrocarbyl groups includethe following:

(1) hydrocarbon substituents, i.e., aliphatic (e.g., alkyl or alkenyl),alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, aromatic-,aliphatic- and alicyclic-substituted aromatic substituents and the likeas well as cyclic substituents wherein the ring is completed throughanother portion of the molecule (that is, for example, any two indicatedsubstituents may together form an alicyclic radical);

(2) substituted hydrocarbon substituents, i.e., those substituentscontaining non-hydrocarbon groups which, in the context of thisinvention, do not alter the predominantly hydrocarbon nature of thesubstituent; those skilled in the art will be aware of such groups(e.g., halo (especially chloro and fluoro), hydroxy, mercapto, nitro,nitroso, sulfoxy, etc.);

(3) heteroatom substituents, i.e., substituents which, while having apredominantly hydrocarbon character within the context of thisinvention, contain an atom other than carbon present in a ring or chainotherwise composed of carbon atoms (e.g., alkoxy or alkylthio). Suitableheteroatoms will be apparent to those of ordinary skill in the art andinclude, for example, sulfur, oxygen, nitrogen and such substituents as,e.g., pyridyl, furyl, thienyl, imidazolyl, etc.

In general, no more than about 2, preferably no more than one, heterosubstituent will be present for every ten carbon atoms in thehydrocarbyl group. Typically, there will be no such hetero atomsubstituents in the hydrocarbyl group. Therefore, the hydrocarbyl groupis purely hydrocarbon.

In one embodiment, the invention relates to a method of separating acoating from a base plastic in a multilayered structure. The coating mayhave more than one layer. The coating may have multiple layers,sometimes up to 5 or more layers. The layers may include ink, adhesive,etc. as well as layers derived from polymers. The method involves thesteps of contacting the multilayered structure with a mixture containinga major amount of water, at least one basic compound or acid compound,at least one lifting agent, and at least one accelerator, and separatingthe coating from the base plastic. In one embodiment, the method uses amixture containing a major amount of water, at least one acid compoundand at least one lifting agent. In a specific embodiment, the inventionrelates to a method of removing a coating involving the steps ofproviding a coated article, contacting the coated article with a mixturecontaining a major amount of water, at least one basic compound or acidcompound, at least one lifting agent, and at least one accelerator, andremoving the mixture and the coating from the polymer article.

The multilayered structure is any structure containing at least onecoating and at least one base plastic. The multilayered structure may ormay not contain: additional polymer layers, and/or additionalnon-polymer layers. Although in a preferred embodiment the coating andbase plastic are next to each other, it is not necessary that thecoating and base plastic are in direct contact with each other. Forexample, an adhesive layer or pigment layer may be interposed betweenthe coating and base plastic.

The coatings for polymer articles, including barrier coatings, aregenerally polymers. In one embodiment, the multilayered structure is acoated plastic container where the coating is a barrier coating andparticularly a gas barrier coating which prevents the loss ofcarbonation of a carbonated beverage contained in a plastic container.In another embodiment, the multilayered structure is a plastic containercontaining at least one coating which is a gas barrier polymer layerthat prevents oxygen or other gases from entering into the plasticcontainer. In yet another embodiment, the multilayered structure is aplastic container containing at least one coating which is a barriercoating that prevents light, such as ultraviolet light, from enteringinto the plastic container. In still another embodiment, themultilayered structure is a plastic container containing at least onecoating which is a coating that provides additional strength and scuffand/or mar-resistance to the plastic container.

The coating may generally be based on thermoplastic or crystallineresins. Specific coatings may be derived from polyvinylidine chloridecopolymer, lower alkyl (such as methyl or ethyl) acrylate/acrylonitrilecopolymer, a copolymer containing an acrylic and methacrylic monomertherein, a polymer or copolymer containing ethlenically unsaturatedmonomer, vinylidine chloride/acrylonitrile copolymer, vinylidinechloride/acrylonitrile/methacrylonitrile copolymer, vinylidinechloride/methacrylonitrile copolymer, vinylidinechloride/acrylonitrile/glycidyl acrylate copolymer, vinylidinechloride/acrylonitrile/glycidyl methacrylate copolymer, vinylidinechloride/acrylonitrile/acrylic monoglyceride copolymer, vinylidinechloride/ethyl acrylate/glycidyl acrylate copolymer, vinylidinechloride/methyl methacrylate/styrene copolymer, vinylidinechloride/acrylonitrile/styrene copolymer, vinylidinechloride/acrylonitrile/trichloroethylene copolymer, vinylidinechloride/acrylonitrile/vinylchloride copolymer, vinylidinechloride/acrylonitrile/methacrylic monoglyceride/trichloroethylenecopolymer, vinylidinechloride/methoxyethylacrylate/methylacrylate/trichloroethylenecopolymer, styrene/butadiene, styrene/alkylacrylate copolymer, alkyland/or aryl esters of unsaturated carboxylic acids such as acrylates andmethacrylates, unsaturated nitriles such as acrylonitrile and/ormethacrylonitrile, vinylhalides such as vinylchloride and vinylbromide,vinylidine chloride and vinylacetate. Other monomers which may beincluded to form barrier coating polymers include vinylchloride,acrylates, methacrylates, unsaturated organic acids such as acrylicmethacrylic itaconic and fumaric acids. In another embodiment, thecoating is a barrier coating derived from polyvinylidine chloride. Thesecoatings are generally described in U.S. Pat. No. 4,573,429, issued toCobbs, Jr. et al., the content of which is hereby incorporated herein byreference. Coatings may also be derived from ethylene-vinyl alcohol.

Additional examples of coatings include those derived from a polymericreaction product of a polyamine and polyepoxide. The coating may also bederived from the reaction product of a polyamine, an alkanolamine, and apolyepoxide. The polyepoxides may be saturated or unsaturated,aliphatic, cycloaliphatic, aromatic, or heterocyclic and may besubstituted or unsubstituted, with noninterfering substituents such ashydroxyl groups or the like. Examples of polyepoxides includepolyglycidyl, ethers of aromatic polyols and polyglycidyl ethers ofpolyhydric aliphatic alcohols. The polyepoxide may have an average1,2-epoxy functionality of at least 1.4 (specifically includingdiepoxides). For example, a polyepoxide may be derived from a diglycidylether of an aromatic polyol such as bisphenol A or an aliphatic alcoholsuch as 1,4-butanediol. Trifunctional and tetrafunctional polyepoxidesmay also be used. Also within the scope of polyepoxides are polyoxalatesor other suitable polycarboxylates. Polyamines include aliphaticpolyamines, aromatic polyamines, ketone blocked polyamines,polyethyleneimines and polyoxyalkaline-polyamines. These polymer layersor coatings are generally described in U.S. Pat. Nos. 5,300,541,5,438,109 and 5,491,204 each issued to Nugent, Jr. et al., the contentsof which are hereby incorporated herein by reference.

The base plastic may be one or more layers. The base plastic may includepigments, adhesive, etc. In one embodiment, the base plastic is free ofpigments. The base plastic may be derived from polyolefins such as highand low density polyethylene and/or polypropylene, polystyrene andstyrene/acrylonitrile copolymers, polyvinyl chloride, vinyl chloridecopolymers, polycarbonates, polyacetals, polyamides and polyesters suchpoly(glycol terephthalates). Additional polymers include those made froma melt-moldable thermoplastic resin by injection molding, blow molding,biaxially drawing blow molding or draw forming and the like. In thisconnection, the polymer article of the barrier-coated polymer articlemay be made of, for example, low density polyethylene, medium densitypolyethylene, high density polyethylene, polypropylene, olefin-typecopolymers such as ethylene/propylene copolymers, ethylene/butenecopolymers, ionomers, ethylene/vinyl acetate copolymers andethylene/vinyl alcohol copolymers, polyesters such as polyethyleneterephthalate (PET), polybutylene terephthalate and polyethyleneterephthalate/isophthalate, polyamides such as Nylon-6, Nylon-6,6 andNylon-6,10, polystyrene, styrene-type copolymers such asstyrene/butadiene block copolymers, styrene/acrylonitrile copolymers,styrene/butadiene/acrylonitrile copolymers (ABS resins), polyvinylchloride, vinyl chloride-type copolymers such as vinyl chloride/vinylacetate copolymers, polymethyl methacrylate and acrylic copolymers suchas methyl methacrylate/ethylacrylate copolymers, polycarbonate,combinations thereof and the like. In a preferred embodiment, the baseplastic is polyethylene terephthalate (PET), polyethylene orpolypropylene.

Methods of separating a coating from a base plastic and in particular abarrier-coating from a polymer article involve contacting themultilayered structure or coated polymer article (or flakes therefrom)with the composition described more fully below. The coating isphysically separated from the base plastic. In the embodiment of apolymer article, the coating is physically separated from the polymerarticle or flakes therefrom.

The multilayered structure may be subject to one or more pretreatmentsteps. For instance, the multilayered structure may be cleaned, dried,heated, cooled and/or pretreated with an activating compound such as amild acidic or basic solution rinsing treatment. Non-plastic debris,such as dirt, adhesives, metal contaminants, and/or paper contaminants,may be removed from the multilayered structures or flakes therefrom. Inone specific embodiment, plastic labelling may also be removed from thecoated polymer articles or flakes therefrom. Alternatively oradditionally, the multilayered structure may be granulated into flakesor small pieces. Hereinafter, when appropriate, reference to themultilayered structure also includes reference to flakes obtainable fromthe multilayered structure. The size of the flakes depends upon thegranulating conditions used. Flake size is not critical to theinvention. Cleaning the multilayered structure may be accomplished byone or more of the following steps. The multilayered structure may besubjected to a steam treatment in an aspirator, washed with cold and/orhot water and/or cleaning solution and/or dried. Washing is especiallyeffective for removing label contaminants and/or residual adhesives.

The multilayered structure is contacted with a separating compositioncontaining a major amount of water, at least one basic compound or acidcompound, at least one lifting agent, and at least one accelerator.Contacting the multilayered structure with the separating compositionmay be accomplished by spraying, flooding, wiping or immersing orotherwise bringing the multilayered structure into contact with theseparating composition.

The multilayered structure is contacted with the separating compositionfor a time sufficient to separate the coating from the base plastic.This time will vary depending on a number of factors including thecomposition of the coating and base plastic, the composition of anyother layer, temperature, the presence or absence of any pretreatmentsteps including precleaning steps, the relative size and form (forexample, flaked or unflaked form) of the multilayered structure, therelative thickness or relative amount of the coating compared to thebase plastic or compared to the remaining portion of the multilayeredstructure, and the like. During or just prior to contact, the separatingcomposition may be agitated to increase the uniformity of theconcentration of the individual components present in the separatingcomposition at various locations around the multilayered structure.Agitation may be accomplished by shaking, stirring, vibrating bymechanical or high-frequency ultrasonic sound waves.

In one embodiment, the multilayered structure is in contact with theseparating composition from about 10 seconds to about 4 hours. Inanother embodiment, the contact time is from about 20 seconds to about 2hours. In a preferred embodiment, the contact time is from about 30seconds to about 60 minutes. In a most preferred embodiment, contacttime is from about 10 minutes to about 40 minutes. The separatingcomposition and one of the coatings are then separated from the baseplastic of the multilayered structure. Although not wishing to be boundby any theory, it is believed the separating composition loosens, liftsand ultimately separates the coating from the base plastic.

Once the coating layer is physically separated from the base plastic orremaining portions of the multilayered structure, further separationand/or collection methods known to those skilled in the art can beimplemented, for instance, using a separation tank such as a settlingtank, a float-sink tank, and a hydrocyclone in addition to in-linefilters. In the embodiment of a coated polymer article immersed in theseparating composition, the coating is separated from the polymerarticle, and the coating or the polymer article can be further separatedand/or collected using methods known to those skilled in the art. Othermethods which further separate different plastics, especially when bothplastics are physically separated yet in the same solution, can be used.Various properties of the individual polymer layers, such as size,specific gravity, density and the like, provide the basis for furtherseparation after initial separation is achieved.

Once the coating layer is further separated from the base plastic orremaining portion of the multilayered structure containing the baseplastic and collected, drying may be implemented. Drying may beaccomplished by mechanical drying or high temperature drying.

Either or both of the isolated polymer layers can be subjected toadditional processing. For instance, in the embodiment of a coatedpolymer article, the polymer article from which the coating has beenremoved can be subsequently used in various recycling processes. Inparticular, the polymer article from which the coating has been removedmay be recycled into beverage containers, food containers, othercontainers, clothing, carpet materials, and fiberfill. Various recyclingmethods are known by those skilled in the art and may include extrusion.

Referring to FIG. 1, an embodiment of a method of separating coatingfrom a base plastic of a multilayered structure, and subsequentlyprocessing base plastic is illustrated. In particular, a method ofrecycling polymer articles having a polymer coating is illustrated.Coated polymer articles 10 are optionally washed in a washing system 12which may involve immersing in hot and/or cold water and then fed to agranulator 14 which converts the coated polymer articles into coatedpolymer flakes. The coated polymer flakes are again optionally cleanedin a washing system 16 which may involve immersing in hot and/or coldwater. The coated polymer flakes are transferred to a separation system18 where they are immersed in a separating composition containing amajor amount of water, at least one basic compound or acid compound, atleast one lifting agent, and at least one accelerator. The separationsystem 18 may contain a means for contacting the coated polymer flakeswith the separating composition and a filtering means to furtherphysically separate the coating from the polymer flakes therebyfacilitating subsequent collection of the polymer flakes. For example,the separating composition containing the coated polymer flakes maycontain a spinning or centerfuge mechanism which spins components, wherethe relatively heavy components, such as the polymer flakes, sink to thebottom so that they may be collected. As a result, the coating issubstantially or completely separated from the polymer flakes, and thepolymer flakes are transferred to a dryer 20. The polymer flakes,substantially free of the coating, may be optionally washed again in awashing system 22, and then are introduced to an extruder 24 whichproduces recycled polymer in any desired form, such as in pelletizedform, from the polymer flakes. The recycled polymer may be washed againin a washing system 26 and then collected as clean recycled polymerpellets 28. Although a number of washing steps are described, eachwashing step is optional so that the entire separating and recyclingprocess may involve none, one, two, three or four or even more washingsteps strategically located throughout the process. If two or morewashing steps are used, each individual washing step may be the same ordifferent from each other washing step.

The separating composition for contacting the multilayered structurecontains a major amount of water. In one embodiment, the separatingcomposition contains greater than about 60% by weight of water. Inanother embodiment, the separating composition contains greater thanabout 70% and less than about 99% by weight of water. In a preferredembodiment, the separating composition contains greater than about 75%by weight of water. In a more preferred embodiment, the separatingcomposition contains about 75% to about 95% by weight of water. Thewater used may be tap water, purified water, or deionized water.

The separating composition for contacting the multilayered structurecontains at least one basic compound or at least one acid compound. Inthis sense, the separating composition contains at least one pHmodifier. The pH modifier, which may be a basic compound or an acidcompound, either increases or decreases the pH of the generally aqueousinventive composition. In the embodiments involving a basic compound,the pH of the inventive composition is greater than about 7.5. Inanother embodiment, the pH of the inventive composition is greater thanabout 8.5, and more preferably greater than about 9. In the embodimentsinvolving an acid compound, the pH of the inventive composition is lessthan about 6.5. In another embodiment, the pH of the inventivecomposition is less than about 5.5, and more preferably less than about5.

In one embodiment, the separating composition for contacting themultilayered structure contains at least one basic compound. As usedherein, the term "basic compound" is intended to include alkali metal,alkaline earth metal and ammonium hydroxides, silicates, phosphates,borates, carbonates, and mixtures thereof, and amines and mixturesthereof. For example, the basic compound includes alkali metalhydroxides, alkaline earth metal hydroxides, ammonium hydroxides, alkalimetal silicates and so on. In one embodiment, the basic compound is"dry" or substantially anhydrous.

Alkali metals include lithium, sodium, potassium, rubidium and cesium.Alkaline earth metals include beryllium, magnesium, calcium, strontium,and barium. Ammonium ions include quaternary ammonium ions representedby Formula (I): ##STR1## where R¹ to R⁴ are individually selected fromhydrogen and alkyl groups containing 1 to about 5 carbon atoms, andhydroxyalkyl containing 1 to about 5 carbon atoms. In a preferredembodiment, R¹ to R⁴ are each hydrogen, methyl or ethyl.

Specific basic compounds include sodium tetraborate, sodium carbonate,sodium bicarbonate, sodium hydroxide, sodium phosphate, sodiumpyrophosphate and other polyphosphates, sodium silicate, potassiumcarbonate, potassium bicarbonate, potassium hydroxide, potassiumphosphate, potassium pyrophosphate and other polyphosphates, ammoniumcarbonate, ammonium hydroxide, ammonium hydrogen phosphate, ammoniumphosphate, calcium carbonate, calcium hydroxide, calcium phosphate,calcium pyrophosphate, calcium silicate, magnesium carbonate, magnesiumhydroxide, magnesium phosphate, magnesium pyrophosphate, magnesiumsilicate, or mixtures of two or more thereof.

Amines include aliphatic amines, cycloaliphatic amines, aromatic aminesand heterocyclic amines. The amine may be a primary, secondary ortertiary amine. In a preferred embodiment, the amine is a tertiaryamine. The amine may be a monoamine, diamine or polyamine. In anotherembodiment, the amine is a hydroxyamine. When the amine is ahydroxyamine, non-hydroxy substituents on the amine nitrogen, whenpresent, may individually be hydrocarbyl groups containing 1 to about 8and preferably 1 to about 5 carbons atoms. Examples of hydroxyaminesinclude hydroxyamines having one or more hydroxyalkyl groups each having1 to about 8 carbon atoms, and preferably 1 to about 5 carbon atoms suchas hydroxymethyl, hydroxyethyl and hydroxybutyl groups. Specificexamples of hydroxyamines include mono-, di- and tri-ethanolamine,3-amino-1-propanol, 2-amino-2-methyl-1-propanol,2-amino-2-ethyl-1,3-propanediol, tris(hydroxymethyl)aminomethane,N-methylethanolamine, 2-diethylamino-2-methyl-1-propanol andtriethanolamine. In a most preferred embodiment, the amine istriethanolamine.

Preferred basic compounds include potassium hydroxide, sodium hydroxide,ammonium hydroxide and triethanolamine. In one embodiment, the inventivecomposition contains the basic compound in an amount from about 1% toabout 25% by weight. In a preferred embodiment, the inventivecomposition contains the basic compound in an amount from about 5% toabout 20% by weight.

In one embodiment, the inventive composition for contacting thebarrier-coated article or flakes therefrom contains at least one acidcompound. As used herein, the term "acid compound" is intended toinclude organic acids such as carboxylic acids containing 1 to about 50and preferably about 2 to about 12 carbon atoms and inorganic acids suchas mineral acids.

Specific examples of inorganic acids include nitric acid, halogen acidssuch as hydrofluoric acid, hydrochloric acid, hydrobromic acid andhydriotic acid, sulfuric acid, sulfurous acid, perchloric acid, boricacid and phosphorous acids such as phosphorous acid and phosphoric acid.Of these inorganic acids, phosphoric acid is preferred.

Organic acids include carboxylic acids and polycarboxylic acids such asalkanoic acids, including formic acid, acetic acid, propionic acid,butyric acid and so on (generally containing 1 to about 10 carbonatoms), dicarboxylic acids, such as oxalic acid, malonic acid, succinicacid and so on (generally containing 1 to about 12 carbon atoms),hydroxyalkanoic acids, such as citric acid (generally containing 1 toabout 10 carbon atoms), organic phosphorous acids such asdimethylphosphoric acid and dimethylphosphinic acid, sulfonic acids suchas hydrocarbylsulfonic acids (containing 1 to about 20 carbon atoms)including methanesulfonic acid, ethanesulfonic acid, 1-pentanesulfonicacid, 1-hexanesulfonic acid, 1-heptanesulfonic acid, aromatic sulfonicacids such as benzenesulfonic acid, tolulenesulfonic acid, etc.Moreover, in some embodiments, two or more of any of the above-describedacids may be used. Preferred organic acids include acetic acid andcitric acid. In one embodiment, the inventive composition contains theacid compound in an amount from about 1% to about 25% by weight. In apreferred embodiment, the inventive composition contains the acidcompound in an amount from about 5% to about 20% by weight.

The separating composition for contacting the multilayered structurecontains at least one lifting agent. The lifting agent is preferably anycompound capable of lifting one polymer layer away from another polymerlayer. In a preferred embodiment, the lifting agent is a surfactant. Thelifting agent may be present in the separating composition in an amountfrom about 0.001% to about 5% by weight. In a preferred embodiment, thelifting agent is present in the separating composition in an amount fromabout 0.005% to about 1% by weight. In an even more preferredembodiment, the lifting agent is present in the separating compositionin an amount from about 0.01% to about 0.1% by weight.

Examples of lifting agents which may be included in the separatingcomposition for contacting the multilayered structure include anionic,cationic, nonionic and amphoteric surfactants. These surfactants areknown in the art, and many of these surfactants are described inMcCutcheon's "Volume I: Emulsifiers and Detergents", 1995, NorthAmerican Edition, published by McCutcheon's Division MCP PublishingCorp., Glen Rock, N.J., and in particular, pp. 1-232 which describes anumber of anionic, cationic, nonionic and amphoteric surfactants and ishereby incorporated by reference for the disclosure in this regard.Examples of useful lifting agents include fluorocarbon surfactants,sulfosuccinate surfactants, alkloxylated alcohols, alkyoxylated phenols,polyoxyalkylene glycols, phosphate esters, aromatic sulfonates,diphenylsulfonates, alkoxylated alkyl aromatics and mixtures thereof.

In a preferred embodiment, especially the embodiments involving a basiccompound, the lifting agent is an anionic surfactant or a cationicsurfactant. In another embodiment, the lifting agent is a fluorocarbonsurfactant, and preferably, an anionic fluorocarbon surfactant.

In a preferred embodiment, especially the embodiments involving an acidcompound, the lifting agent is a nonionic surfactant. In anotherembodiment, especially the embodiments involving an acid compound, thelifting agent is an alkoxylated alkylaromatic surfactant.

Fluorocarbon surfactants, such as metal or ammonium fluorocarbonsulfonates or carboxylates, are commercially available from the 3MCompany under the general trade designation "Fluorad" and from DuPontunder the general trade designation "Zonyl." Specific Fluoradsurfactants include potassium fluorinated alkyl carboxylates, ammoniumperfluoro alkyl sulfonates, potassium perfluoro alkyl sulfonates, amineperfluoro alkyl sulfonates, and ammonium perfluoro alkyl carboxylates.Fluorocarbon surfactants include alkali metal, ammonium and aminefluorinated alkyl sulfonates and carboxylates. Specific Fluoradsurfactants include those under the designation FC-109, FC-121, FC-93,FC-95, FC-98, FC-99, FC-120, FC-129 and FC-143. Specific Zonylsurfactants include Zonyl FSA, Zonyl FSE, Zonyl FSJ, Zonyl FSP, ZonylNF, Zonyl RP, Zonyl TBS and Zonyl UR.

In another embodiment, the lifting agent is a sulfosuccinate surfactantor a derivative thereof such as a hydrocarbyl substituted sulfosuccinatewhere each hydrocarbyl group contains 1 to about 24 and preferably 1 toabout 12 carbon atoms. In a preferred embodiment, the lifting agent isan anionic sulfosuccinate surfactant or a derivative thereof.Sulfosuccinates include alkali metal alkyl sulfosuccinates where thealkyl group contains 1 to about 24 and preferably 1 to about 12 carbonatoms such as sodium dioctyl sulfosuccinates. Sulfosuccinate surfactantsare commercially available from Union Carbide under the general tradedesignation "Triton®" and specifically Triton® GR-5M and Triton® GR-7M.

In another embodiment, the lifting agent is a modified alkoxylatedsurfactant. In a preferred embodiment, the lifting agent is an anionicmodified ethoxylate surfactant. Modified alkoxylated surfactants includealkoxylated alcohols, and alkoxylated phenols. In one embodiment, thealkoxylated alcohol includes ethoxylated and propoxylated alcoholshaving from 1 to about 30 carbon atoms, or from about 4 to about 24carbon atoms, or from about 6 to about 18 carbon atoms. These materialsmay be prepared by reacting an alcohol with an alkylene oxide such asethylene oxide or propylene oxide. Modified ethoxylates surfactants areethoxylated alcohols commercially available from Union Carbide under thegeneral trade designation "Triton®", and specifically Triton® DF-12,DF-16, DF-18, and DF-20.

In another embodiment, the lifting agent is hydrocarbylphenolalkoxylate, such as an alkylphenol ethoxylate surfactant. Thehydrocarbyl group may contain 1 to about 24 and preferably 2 to about 18carbon atoms. The hydrocarbylphenol alkoxylates include alkylphenolethoxylates and propoxylates. Examples of alkylphenol alkoxylatesinclude octylphenoxy polyethoxyethanol and nonylphenol ethoxylate. Thesematerials are available from Union Carbide under the trade designationTriton®, N-42, N-57 and N-101. An alkylphenol ethoxylate surfactant maybe an anionic surfactant or a nonionic surfactant. Specific examplesinclude alkylpolyethylene glycol ether acetic acid, and ethoxylateanionic complexes. Specific compounds are commercially available fromSandoz Chemicals under the general trade designation "Sandopan" and fromHulls America under the general trade designation "Marlowet."

In another embodiment, the surfactant is a polyoxyalkylene glycol.Polyoxyalkylene glycols include polyoxyethylene and polyoxypropyleneglycols. Examples of these materials are available from Union Carbideunder the tradename Carbowax® Peg 300, 600, 1000 and 1450, and NIAX 425and 1025.

In another embodiment, the lifting agent is a phosphate ester surfactantsuch as an alkali metal phosphate. In a preferred embodiment, thelifting agent is an anionic phosphate ester surfactant where the esterhydrocarbyl moiety each independently containing 1 to about 24 andpreferably 1 to about 12 carbon atoms. In another preferred embodiment,the surfactant is the potassium salt of a phosphate ester. Examples ofcommercially available phosphate ester surfactants include those fromUnion Carbide under the trade designation "Triton®", and specificallyTriton® H-55 and Triton® H-66.

In another embodiment, the lifting agent is an aromatic sulfonatesurfactant, such as a naphthalene sulfonate or hydrocarbyl substitutednaphthalene sulfonate surfactant, a benzene or hydrocarbyl substitutedbenzene sulfonate surfactant, an anthracene or hydrocarbyl substitutedanthracene sulfonate and a phenyl or hydrocarbyl substituted phenylsulfonate. In each case, the hydrocarbyl group contains 1 to about 24and preferably 1 to about 12 carbon atoms. In a preferred embodiment,the lifting agent is an anionic alkyl naphthalene sulfonate surfactant.Examples include naphthalene and alkyl naphthalene alkali metalsulfonates such as naphthalene and alkyl naphthalene sodium sulfonates.Specific alkyl naphthalene sulfonates commercially available includethose from Witco under the general trade designation "Petro®" and fromHenkel under the general trade designation "Sellogen."

In another embodiment, the lifting agent is a diphenyl sulfonate orderivative thereof. In a preferred embodiment, the lifting agent is ananionic diphenyl sulfonate surfactant or a hydrocarbyl substitutedderivative thereof where the hydrocarbyl group contains 1 to about 24and preferably 1 to about 12 carbon atoms. Specific examples includealkali metal alkyl diphenyl oxide disulfonates such as sodiumhexyldiphenyloxide disulfonate, sodium decyldiphenyloxide disulfonate,dodecyldiphenyloxide disulfonic acid, sodium dodecyldiphenyloxidedisulfonate, N-decyldiphenyloxidedisulfonate, sodiumn-decyldiphenyloxidedisulfonate and sodium n-hexadecyldiphenyloxidedisulfonate. Diphenlysulfonate surfactants are commercially availablefrom Dow under the general trade designation "Dowfax," and specificallyinclude Dowfax C6L, C10L, 2A0, 2A1, 2A1-D, 2EP, 3B0, 3B2, 3B2-D, 2000,8390, and 8390-D.

The separating composition for contacting the multilayered structurecontains at least one accelerator. The accelerator, in combination withthe other components of the composition, accelerates the separation ofcoating from base plastic in a multilayered structure and in onespecific embodiment, a barrier coating from a polymer article. Suitableaccelerators include glycol ethers, glycol ether acetates (which may beanalogous to the glycol ethers discussed below), alkylene carbonates,glycerine, lactones and hydrocarbyl substituted lactones, pyrrolidonesand hydrocarbyl substituted pyrrolidones, furan compounds and the likewhere the hydrocarbyl groups contain 1 to about 24 and preferably 2 toabout 18 carbon atoms.

In one embodiment, glycol ethers include alkylene glycol mono- anddi-alkyl ethers (where the alkyl and alkylene groups contain from 1 toabout 12 and preferably 1 to about 8 carbon atoms). Glycol ethersspecifically include ethylene, polyethylene such as diethylene,propylene, and polypropylene such as dipropylene glycol mono- anddialkylethers. Glycol ethers may be represented by ##STR2## where R₁,R₂, R₄ and R₅ are each independently hydrogen or hydrocarbyl groupscontaining 1 to about 8 and preferably 1 to about 5 carbon atoms, R₃ isan alkylene group containing 1 to about 8 and preferably 1 to about 5carbon atoms, and x is 1 to about 20 and preferably 1 to about 3. Inparticular, glycol ethers include ethylene glycol ethers, propyleneglycol ethers, butylene glycol ethers, di(ethylene glycol) ethers,di(propylene glycol) ethers, di(butylene glycol) ethers, tri(ethyleneglycol) ethers, tri(propylene glycol) ethers, tri(butylene glycol)ethers and other poly(ethylene, propylene or butylene) glycol ethers.Glycol ethers also include ethylene, polyethylene, propylene andpolypropylene mono- and diphenylethers such as ethylene glycol monophenyl ether.

Specific examples of glycol ethers include ethylene glycol methyl ether,ethylene glycol methylbutyl ether, ethylene glycol ethylbutyl ether,ethylene glycol ethyl ether, ethylene glycol butyl ether, ethyleneglycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycoldibutyl ether, propylene glycol methyl ether, propylene glycol ethylether, propylene glycol butyl ether, propylene glycol dimethyl ether,propylene glycol diethyl ether, propylene glycol dibutyl ether,di(ethylene glycol) methyl ether, di(ethylene glycol) ethyl ether,di(ethylene glycol) butyl ether, di(ethylene glycol) hexyl ether,di(ethylene glycol) dimethyl ether, di(ethylene glycol) diethyl ether,di(ethylene glycol) dibutyl ether, di(ethylene glycol) butylmethylether, di(ethylene glycol) dodecyl ether, di(propylene glycol) methylether, di(propylene glycol) butyl ether, tri(ethylene glycol) methylether, tri(ethylene glycol) dimethyl ether, tri(propylene glycol) methylether, tri(propylene glycol) butyl ether, and mixtures thereof. Glycolethers are available from Union Carbide under the name Cellosolve®, DowChemical under the name Dowanol® and Arco Chemical under the nameArcosolv. Preferred glycol ethers include propylene glycol butyl ether,di(ethylene glycol) butyl ether and di(propylene glycol) methyl ether.

Lactones and hydrocarbyl substituted lactones include alkyl lactoneswhere the alkyl group contains 1 to about 8 carbon atoms, such asbutyrolactone and gamma-butyrolactone. Pyrrolidones and hydrocarbylsubstituted pyrrolidones include alkyl pyrrolidones where the alkylgroup contains 1 to about 8 carbon atoms, such asN-methyl-2-pyrrolidone. Furan compounds include furfuryl alcohol,tetrahydrofurfuryl alcohol, and analogs thereof. Alkylene carbonatescontain 1 to about 16 and preferably 1 to about 8 carbon atoms in thealkylene moiety and specifically include dimethyl carbonate, diethylcarbonate, ethylene carbonate and dipropyl carbonate.

Glycol ether acetates may be prepared by reacting acetic acid or a saltor derivative thereof with one or more of the glycol ethers describedabove. Glycol ether acetates generally include ethylene glycol etheracetates, propylene glycol ether acetates, butylene glycol etheracetates, di(ethylene glycol) ether acetates, di(propylene glycol) etheracetates, di(butylene glycol) ether acetates, tri(ethylene glycol) etheracetates, tri(propylene glycol) ether acetates, tri(butylene glycol)ether acetates and other poly(ethylene, propylene or butylene) glycolether acetates. Glycol ether acetates specifically include ethyleneglycol butyl ether acetate, propylene glycol methyl ether acetate,di(ethylene glycol) ethyl ether acetate and di(propylene glycol) methylether acetate.

The accelerator is present in the separating composition in an amountfrom about 1% to about 20% by weight. In a preferred embodiment, theaccelerator is present in the separating composition in an amount fromabout 2% to about 15% by weight. In a most preferred embodiment, theaccelerator is present in the separating composition in an amount fromabout 3% to about 10% by weight. In one embodiment, only one acceleratoris present in the separating composition. In a preferred embodiment, atleast two accelerators are present in the separating composition. Inanother embodiment, at least three accelerators are present in theseparating composition. In another embodiment, one glycol ether isincluded in the separating composition with or without otheraccelerators. In another embodiment, at least two glycol ethers areincluded in the separating composition with or without otheraccelerators. In yet another embodiment, at least three glycol ethersare used in the separating composition with or without otheraccelerators. In one embodiment, the separating composition containsfrom about 1% to about 10% by weight of a glycol ether. In a preferredembodiment, the separating composition contains from about 2% to about8% by weight of a glycol ether.

The separating composition may optionally include one or more of thefollowing additives: rinse aids, water softeners, foamers, defoamers,and antifoamers. The additives may be present in the separatingcomposition in an amount from about 0.001% to about 5% by weight. In apreferred embodiment, the additives are present in the separatingcomposition in an amount from about 0.01% to about 1% by weight.

Antifoamers reduce or prevent the formation of stable foam and includesilicones or organic polymers. Examples of these and additionalantifoamers are described in "Foam Control Agents," by Henry T. Kerner(Noyes Data Corporation, 1976), pages 125, 162.

Defoamers are compounds which control the foaming tendencies of acomposition. Examples of organic solvents which are effective defoamersinclude xylene, mesitylene, benzene, aromatic petroleum spirits, methylisobutyl ketone, mineral spirits and mixtures thereof.

Foamers are additives which release gas to expand a given material byforming closed bubbles or cause frothing. Examples of foamers which maybe incorporated into the separating composition for contacting abarrier-coated article or flakes therefrom include polyphosphates, EDTA,gluconates, citrates and the like.

The temperature at which the separating composition is used is anytemperature effective to separate one polymer layer from another polymerlayer. In one embodiment, the temperature of the separating compositionis in the range from about 40° F. to about 212° F. In anotherembodiment, the temperature at which the separating composition is usedis in the range from about 70° F. to about 210° F. In anotherembodiment, the temperature at which the separating composition is usedis in the range from about 80° F. to about 200° F. In a preferredembodiment, the temperature at which the separating composition is usedis in the range from about 100° F. to about 190° F.

While not intending to be limiting, the following examples illustratethe separating compositions and methods of using such compositions.Unless otherwise indicated in the following examples and elsewhere inthe specification and claims, all parts and percentages are by weight,all temperatures are in degrees Centigrade, and pressure is at or nearatmospheric pressure.

EXAMPLE 1

A composition is prepared containing 15 weight percent dry potassiumhydroxide, 0.01 weight percent of a fluorinated alkyl carboxylateidentified as Fluorad FC-109 from 3M, 0.02 weight percent of sodiumdioctyl sulfosuccinate identified as Triton® GR-5M from Union Carbide, 2weight percent of dipropylene glycol methyl ether, 2 weight percentpropylene glycol n-butyl ether and the balance water. The temperature ofthe bath is maintained at about 150° F.

EXAMPLE 2

A composition is prepared containing 12 weight percent ammoniumhydroxide, 0.8 weight percent ethylene glycol butyl ether acetate, 0.004weight percent of a ammonium perfluoro alkyl sulfonate identified asFluorad FC-121 from 3M, 0.002 weight percent of alkyl naphthalene sodiumsulfonate identified as Petro® P from Witco, 1.5 weight percent ofpropylene glycol butyl ether, 2.7 weight percent ethylene glycolethylbutyl ether and the balance water. The temperature of the bath ismaintained at about 155° F.

EXAMPLE 3

A composition is prepared containing 18 weight percent sodium hydroxide,0.007 weight percent of sodium hexyldiphenyloxide disulfonate identifiedas Dowfax C6L from Dow Chemical, 0.04 weight percent of Triton® H-55 (aphosphate ester), 2.5 weight percent of diethylene glycol ethyl ether,13.5 weight percent propylene glycol methyl ether acetate and thebalance water. The temperature of the bath is maintained at about 175°F.

EXAMPLE 4

A composition is prepared containing 3 weight percent dry potassiumhydroxide, 0.06 weight percent of a potassium fluorinated alkylcarboxylate identified as Fluorad FC-129 from 3M, 5 weight percent ofgamma-butyrolactone, 6 weight percent propylene glycol dimethyl etherand the balance water. The temperature of the bath is maintained atabout 110° F.

EXAMPLE 5

A composition is prepared containing 25 weight percent triethanolamine,0.005 weight percent of an amine perfluoro alkyl sulfonate identified asFluorad FC-99 from 3M, 0.2 weight percent of sodium dioctylsulfosuccinate identified as Triton® GR-7M from Union Carbide, 0.09weight percent of alkyl naphthalene sodium sulfonate identified asPetro® 11 from Witco, 1 weight percent of dipropylene glycol methylether, 1 weight percent N-methyl-2-pyrrolidone, 1 weight percentdipropyl carbonate and the balance water. The temperature of the bath ismaintained at about 120° F.

EXAMPLE 6

A composition is prepared containing 5 weight percent dry potassiumhydroxide, 2 weight percent potassium phosphate, 0.01 weight percent ofTriton® DF-20 (an anionic modified ethoxylate), 0.4 weight percent ofsodium dioctyl sulfosuccinate identified as Triton® GR-7M from UnionCarbide, 1 weight percent of diethylene glycol methyl ether, 1 weightpercent ethylene carbonate and the balance water. The temperature of thebath is maintained at about 200° F.

EXAMPLE 7

A composition is prepared containing 15 weight percent dry potassiumhydroxide, 0.01 weight percent of a fluorinated alkyl carboxylateidentified as Fluorad FC-109 from 3M, 0.02 weight percent of sodiumdioctyl sulfosuccinate identified as Triton® GR-5M from Union Carbide, 2weight percent of dipropylene glycol methyl ether, 2 weight percentpropylene glycol n-butyl ether and the balance water. The temperature ofthe bath is maintained at about 190° F.

EXAMPLE 8

A composition is prepared containing 20 weight percent sodium borate, 1weight percent of a fluorinated alkyl carboxylate identified as FluoradFC-129 from 3M, 0.02 weight percent of sodium dioctyl sulfosuccin ateidentified as Triton® GR-7M from Union Carbide, 10 weight percent ofdipropylene glycol methyl ether, and the balance water. The temperatureof the bath is maintained at about 205° F.

EXAMPLE 9

A composition is prepared containing 2.5 weight percent citric acid, 0.2weight percent of octylphenol ethoxylate identified as Delonic OPE-10from DeForest Enterprises, 5 weight percent of di(ethylene glycol) butylether, and the balance water. The temperature of the bath is maintainedat about 150° F.

EXAMPLE 10

A composition is prepared containing 2.5 weight percent phosphoric acid,0.2 weight percent of an ethoxylated linear alcohol identified asMarlowet BL from Huls America, 5 weight percent of di(ethylene glycol)butyl ether, and the balance water. The temperature of the bath ismaintained at about 150° F.

An example of a method of recycling multilayered structures and inparticular, coated polymer articles, is described as follows. PET foodand beverage containers coated with a gas barrier coating derived frompolyamine, alkanolamine and polyepoxide are fed to a granulator whichconverts the coated PET containers into coated PET flakes. The coatedPET flakes are cleaned in a washing system which involves sequentiallyimmersing in hot and then cold water baths. The coated PET flakes aredried and transferred to a separation system where they are immersed ina composition according to Example 1 or 9 above. As a result, the gasbarrier coating is substantially or completely separated from the PETflakes, and the PET flakes are filtered away from the separated coatingand then transferred to a dryer. The PET flakes, substantially free ofthe gas barrier coating, are dried and then introduced to an extruderwhich produces recycled PET in pelletized form from the polymer flakes.The resultant PET pellets are substantially clear and do not exhibitextensive coloring or opaqueness.

Although the invention has been shown and described with respect to anexemplary embodiment thereof, it is obvious that equivalent alterationsand modifications will occur to those skilled in the art upon readingand understanding the specification. The present invention includes allsuch equivalent alterations and modifications, and is limited only bythe scope of the following claims.

We claim:
 1. A method of physically separating a gas barrier polymercoating from a base thermoplastic polymer in a multilayered structure,comprising the steps of:(A) providing the multilayered structurecomprising at least one gas barrier polymer coating and at least onebase thermoplastic polymer; (B) contacting the multilayered structurewith a mixture comprising (i) a major amount of water, (ii) at least onecompound selected from the group consisting of a basic compound and anacid compound, (iii) at least one lifting agent, and (iv) at least oneaccelerator; wherein the pH of the mixture in step (B) is less thanabout 6.5; and (C) physically separating the gas barrier polymer coatingfrom the base thermoplastic polymer.
 2. The method of claim 1 whereinthe acid compound is at least one of an organic acid and an inorganicacid.
 3. A method of physically separating a gas barrier polymer coatingfrom a base thermoplastic polymer in a multilayered structure,comprising the steps of(A) providing the multilayered structurecomprising at least one gas barrier polymer coating and at least onebase thermoplastic polymer; (B) contacting the multilayered structurewith a mixture comprising (i) a major amount of water, (ii) at least oneacid compound, and (iii) at least one lifting agent; and (C) physicallyseparating the gas barrier polymer coating from the base thermoplasticpolymer.
 4. The method of claim 3 wherein the multilayered structure isa polyethylene terephthalate container having a polymer coating.
 5. Themethod of claim 3 wherein the acid compound is an organic acid or aninorganic acid.
 6. The method of claim 3 wherein the lifting agent isselected from the group consisting of fluorocarbon surfactants,sulfosuccinate surfactants, alkoxylated alcohols, alkoxylated phenols,polyoxyalkylene glycols, phosphate esters, aromatic sulfonates,diphenylsulfonates, alkoxylated alkyl aromatic surfactants and mixturesthereof.
 7. The method of claim 3 wherein the accelerator is selectedfrom the group consisting of glycol ethers, glycol ether acetates,alkylene carbonates, glycerine, lactones and substituted lactones,pyrrolidones and substituted pyrrolidones, furan compounds and mixturesof two or more thereof.
 8. A composition comprising (i) a major amountof water, (ii) at least one acidic compound, (iii) at least one liftingagent, and (iv) at least one accelerator.
 9. The composition of claim 8having a pH less than about 6.5.
 10. The composition of claim 8 whereinthe lifting agent is selected from the group consisting of fluorocarbonsurfactants, sulfosuccinate surfactants, alkoxylated alcohols,alkoxylated phenols, polyoxyalkylene glycols, phosphate esters, aromaticsulfonates, diphenylsulfonates, alkoxylated alkyl aromatic surfactantsand mixtures thereof.
 11. The composition of claim 8 wherein theaccelerator is selected from the group consisting of glycol ethers,glycol ether acetates, alkylene carbonates, glycerine, lactones andsubstituted lactones, pyrrolidones and substituted pyrrolidones, furancompounds and mixtures of two or more thereof.
 12. The composition ofclaim 8 wherein water (i) is present in an amount greater than about 60%by weight, the acid compound (ii) is present in an amount from about 1%up to about 25% by weight, the lifting agent (iii) is present in anamount from about 0.001% up to about 5% by weight, and the accelerator(iv) is present in an amount from about 1% up to about 20% by weight.13. A method of recycling coated polymer containers comprising the stepsof:(A) providing a polymer container having a polymer coating; (B)preparing flakes from the coated polymer container; (C) contacting theflakes with a mixture comprising (i) a major amount of water, (ii) atleast one compound selected from the group consisting of at least oneacid compound, (iii) at least one lifting agent and (iv) at least oneaccelerator; and (D) separating the mixture and the polymer coating fromthe flakes.
 14. The method of claim 13 wherein the polymer container isa polyethylene terephthalate food or beverage container.
 15. The methodof claim 13 wherein the accelerator is selected from the groupconsisting of glycol ethers, glycol ether acetates, alkylene carbonates,glycerine, lactones and substituted lactones, pyrrolidones andsubstituted pyrrolidones, furan compounds and mixtures of two or morethereof.
 16. The method of claim 13 further comprising the step of (F)extruding the flakes into a food or beverage container.